1. Field of the Invention
The invention is directed to a stator for an electric machine with a ring-shaped stator yoke at which a plurality of stator coils having coil ends are arranged, and with a wiring arrangement for the stator coils at a front side of the stator yoke, wherein the wiring arrangement has connection conductors which are electrically insulated relative to one another and are concentric to one another. The invention also relates to methods for producing a wiring arrangement of a stator.
2. Description of the Related Art
Known stators for electric machines have a stator yoke with a quantity of stator teeth which hold the electric winding, e.g., in the form of individual stator coils which are wound from an insulating wire. The ends of the coils are associated with individual strands and are wired together in a predetermined manner by shared connection conductors. In three-phase generators, the stator has three strands and, therefore, at least three connection conductors to which current is applied at a 120-degree phase offset. The connection conductors are fed to a switch box for connecting the electric machine to a source of electric power.
U.S. Pat. No. 6,369,473 discloses a stator for an electric machine in which the wiring arrangement has electrically insulated connection conductors allocated to each other in concentric manner (see FIG. 7 of the present patent application). The terminals for the ends of the stator coils are formed at the connection conductors as terminal extensions projecting from the latter. The electrical connection can be carried out by a joining technique such as welding, soldering and/or simple winding around the terminal extensions. The connection conductors are supported mutually and at the stator by means of insulating center strips arranged therebetween.
In one of the joined connections mentioned above, it is disadvantageous that the process heat introduced for connecting can result in damage to the insulation between the connection conductors and, further, to the insulation of the wound wires in the area of the coils. This can lead very quickly to unwanted short circuiting which influences the operation of the electric machine and can even lead its outage. Further, damage to the insulation arranged between the connection conductors cancels the fixed position of the connection conductors, which are then no longer arranged at the stator in such a way that reliable operation is ensured. Vibrations which occur during the operation of the electric machine or which act on the latter from the outside lead to mechanical alternating loads on the electrical connections of the machine which can loosen within a short period of time. Winding around the terminal extensions is a typical manual work step which impedes increased efficiency in the manufacture of such stators. Because of the relatively large number of coil ends, there is a considerable risk of faulty connections in the wiring of the coils of a stator due to incorrect allocation to the connection conductors. Even when great caution is exercised in this regard, 100 percent certainty can not be achieved in the manufacture of stators.
It is the object of the present invention to improve a stator constructed in the manner described above in such a way that particularly its wiring arrangement is designed more simply and can be produced, at the same time, by safe processes and in an automated manner. In a further aspect of the invention, methods are provided for producing a wiring arrangement of a stator.
According to a first solution, the invention is based on the arrangement of receiving chambers at the stator which are suitable for mechanically fixing the connection conductors in position and for carrying out the electrical connections of the coil ends to the respective connection conductors. In this way, the assembly steps comprising mechanical fixation of the connection conductors and electrical connection of the latter to the coil ends, which were originally two independent assembly steps, are combined in one individual step so that considerable time and cost are saved in the production of the stator.
According to a second solution, the connection conductors are not connected directly to the coil ends; rather separate plug-in contacts are arranged between the coil ends and the connection conductors. In this way, individual coils can be checked for proper functioning before they are arranged at the stator, and defective coils can be excluded from the continued assembly process. This prefabrication by means of inexpensive and easily fitted plug-in contacts makes it possible to economize on manufacturing costs and manufacturing time and accordingly reduces the return of defective stators at the same time.
In an advantageous construction, the receiving chambers have receiving means for the coil ends. The coil ends can accordingly also be brought into a predetermined position for contacting at the receiving chamber. This step aims at high reproducibility of the electrical connection points between the coil ends and the connection conductors.
Assembly is further simplified in that the receiving chambers are arranged on partial circles which substantially correspond to those of the connection conductors. In this case, for example, a circular connection conductor can simply be attached to an axial side of the stator, wherein the terminals of the connection conductor are simultaneously introduced into the corresponding receiving chambers and a plurality of desired electric clamping connections are also produced simultaneously.
In a particularly advantageous further development, the terminals of the connection conductors are constructed as piercing or cutting clamps. In this way, a cutting clamp connection, known in electrical connection technology, is realized with respect to the coil ends. A particularly noteworthy advantage is that the cutting clamp displaces the insulating sleeve of the coil ends when producing the connection, which obviates any additional steps for removing the insulating sleeve. Accordingly, unintended removal of the insulation sleeve at unwanted locations is excluded.
In repairs, the use of reusable cutting clamps enables fast and simple detachment of the electrical connection, e.g., to a defective coil or damaged connection conductor.
The cutting clamps are advantageously fixed in the receiving chambers by locking elements, for which purpose the terminals of the connection conductors and/or the receiving chambers include barbs or spring elements. Accordingly, when placed on an axial side of the stator, the connection conductors enter into a self-locking mechanical connection with the stator, so that it is not necessary to use additional connections such as screw connections or rivet connections.
It is likewise advantageous when the plug-in contacts and/or the receiving chambers comprise locking elements in the form of barbs or spring elements.
The number of receiving chambers associated with a coil end advantageously corresponds to the quantity of connection conductors. This ensures that the wiring remains changeable, that is, the coil ends can enter into an electrical connection with all connection conductors depending on the applied wiring plan.
It has proven advisable to form the receiving chambers at the bobbins. In this way, a simple and fixed allocation of positions of the coil ends to the receiving chambers is achieved.
Following the concentric arrangement of the common connection conductors, it is likewise useful to arrange the receiving chambers associated with a coil end at the stator radially with respect to one another.
The electrical connection points of the coil ends with the terminals of the connection conductors are preferably arranged within the interior of open chambers formed by the receiving chambers for protection against external influences.
Similarly, the electrical connection points of the coil ends with the plug-in contacts are advantageously arranged in the interior of the chambers.
In another advantageous variant of the invention, the connection conductors and the stator have reference features which determine the position of the connection conductors relative to the ends of the stator coils, and the terminals are so formed at the connection conductors and/or the receiving chambers are so formed at the stator that they correspond in pairs exclusively to predetermined positions at the stator after the allocation of position has been accomplished. In this way, a quantity of electrical connections is defined in a definite manner for a predetermined wiring plan and errors are reliably excluded.
In an analogous manner, it is also advantageous according to the second solution when the connection conductors and the stator have reference features which determine the position of the connection conductors relative to the ends of the stator coils, and the mating elements are formed at the connection conductors and/or the plug-in contacts elements are formed at the stator in such a way that they correspond in pairs exclusively to predetermined positions at the stator after mutual allocation of position has been accomplished.
In an advantageous construction, the plug-in contacts also have cutting clamps for forming a cutting clamp connection with the coil ends.
The plug-in contacts are constructed, for example, as known flat contacts or spring contacts.
The connection of the connection conductors to the plug-in contacts is substantially simplified during assembly when the plug-in contacts and the receiving means of the connection conductors have play in circumferential direction with respect to the arrangement at the stator.
According to a second feature of the invention, a method for producing a wiring arrangement of a stator has the following essential steps:
arranging the stator coils at the stator yoke;
aligning the coil ends to the receiving chambers;
allocating the position of the connection conductors to the stator;
inserting the terminals of the connection conductors into the receiving chambers, wherein the coil ends are electrically clamped to the terminals of the connection conductors.
In another method for producing a wiring arrangement of a stator, the following steps are carried out:
aligning coil ends to the receiving chambers;
inserting of the plug-in contacts into the receiving chambers, wherein the plug-in contacts are electrically clamped with the coil ends;
arranging the stator coils at the stator yoke;
allocating the position of the connection conductors to the stator;
connecting the mating elements of the connection conductors to the plug-in contacts, wherein the latter enter into an electrical connection with the connection conductors and, in so doing, fix the connection conductors in their position.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.